Underground shelters for the protection of people and of things from hurricanes and tornados are known to those skilled in the art as evidenced by the following Patents:
______________________________________ Design 241,737 2,968,130 3,974,599 Design 242,446 3,049,835 4,642,952 Design 261,432 3,159,117 4,660,334 3,212,220 ______________________________________
In many parts of the United States, an underground shelter is considered impractical because the water table sometimes rises near the surface of the ground, and consequently the shelter becomes saturated with moisture although the shelter may be only 7-12 feet in height and therefore buried not very deep below the surface. Heretofore, others have attempted to provide a prefabricated shelter which can be directly buried in soil saturated with water, and invariably the shelter will eventually deteriorate sufficiently to break or crack and admit moisture thereinto. This is especially so of concrete shelters that inherently shrink over a projected time period and ultimately crack. Furthermore, it is difficult to prevent a thin membrane concrete structure from becoming saturated with the surrounding moisture and thereby raising the humidity within the structure to a value that renders the interior unsuitable for use as a habitation. It is therefore difficult to provide a ready-made underground shelter of the foregoing type having an environment that is always ready to accept persons and things, and wherein things can be stored until needed without degradation due to moisture.
Another important consideration of an underground shelter is the probability of intrusion of water to the extent that the shelter is floated from its underground location towards the surface of the ground where it can be swept away by tornadic winds.
Underground shelters are difficult to build insitu. This is especially so for a spherical, thin membrane, fiberglass structure. On the other hand, fabricating a spherical structure at a manufacturing facility and then transporting the structure to its burial site requires that the shelter be of great structural integrity so that it can be lifted onto a transport, endure the travel, and subsequently again be lifted and deposited within an excavation or hole. Further, the physical size of the shelter must be within the limits set by the law in order for a vehicle to legally transport the shelter along public roads without interference from the bureaucracy.
Heretofore, fiberglass tornado shelters of unitary construction have been suggested; however, the provision of a unitary fiberglass tornado shelter that overcomes all of the above drawbacks and which endures for a reasonable number of years is yet to be achieved until the present invention.
Accordingly, the subject of the present invention is the provision of a novel prefabricated tornado shelter for safely housing and protecting people and things underground, and provides a safe enclosure which is rigidified and built in a unique manner, and which can be anchored to the surrounding subsoil in a new and unobvious manner.